My hamstrings are eternally tight. I came across this tidbit of information that makes sense to me. I also Googled/Bingod (Bongod? Boingod?) to verify.

Are any standing hamstring stretches effective?

You can’t stretch your hamstrings standing in any position. If your leg is weight bearing and you lean forward from the pelvis, the hamstrings contract involuntarily to stabilize your pelvis and prevent gravity from pulling your body forward. This proprioceptive response to gravity and balance is a reflex response that you can’t prevent. You cannot relax the hamstring muscles as long as you are holding that position.

The standing toe-touch and the ballet bar stretch are both bad stretches that can cause damage to the hamstrings, as well as other structures like the lumbar spine ligaments and sciatic nerve.